Non-conjugated chenodeoxycholate induces severe mitochondrial damage and inhibits bicarbonate transport in pancreatic duct cells

Research trends on traditional Chinese medicine and acute pancreatitis: A bibliometric analysis from 2007 to mid-2023

Traditional Chinese Medicine (TCM) is a unique medical system of historic significance, holding substantial influence within China and beyond. In recent years, the efficacy of TCM in treating acute pancreatitis has been substantiated. Despite over two decades of development in this domain, a bibliometric analysis illustrating TCM's role in acute pancreatitis remains scarce.

OBJECTIVE

This study aims to conduct a comprehensive analysis of findings in the field of acute pancreatitis and TCM using machine learning and text-analyzing methodologies. The intent is to provide scientific and intuitive support to researchers and clinicians.

METHODS

We searched the Web of Science Core Collection database for publications and related literature from 2007 to mid-2023. Tools such as Excel, Citespace V, and Vosviewer were utilized for bibliometric analysis. That included assessing published and cited counts, co-authorship mapping, co-citation analysis, burst detection, and keyword analysis.

RESULTS

The study revealed a fluctuating growth trend in the number of publications and citations since 2007. As many as 147 institutions from 13 countries, with a total of 756 authors, have published 202 papers in 76 academic journals. Sichuan University in China and Tang Wenfu have been recognized as the most influential national institution and author. The most frequently published journal is "Pancreas", while the most cited is the "World Journal of Gastroenterology". Commonly used single herbs in this field include Baicalin, Emodin, Rhubarb, and Salvia miltiorrhizae. Frequently used herbal formulations include Da chengqi decoction, Chaiqin chengqi decoction, and Qing yi decoction. Current research hotspots primarily surround concepts like hmgb1, nf-kappab, nfr2, oxidative stress, exosomes, nlrp3, pyroptosis, etc. Potential future research themes could relate to pharmacology, reducing hmgb1, inflammatory response, cell activation, Qing Yi-decoction, etc. This review holds significant guiding importance for clinical and scientific research into TCM treatment for acute pancreatitis in the future.

The role of Ca2+ signalling in the pathology of exocrine pancreas

Exocrine pancreas has been the field of many successful studies in pancreatic physiology and pathology. However, related disease - acute pancreatitis (AP) is still takes it toll with more than 100,000 related deaths worldwide per year. In spite of significant scientific progress and several human trials currently running for AP, there is still no specific treatment in the clinic. Studies of the mechanism of initiation of AP have identified two crucial conditions: sustained elevations of cytoplasmic calcium concentration (Ca2+ plateau) and significantly reduced intracellular energy (ATP depletion). These hallmarks are interdependent, i.e., Ca2+ plateau increase energy demand for its clearance while energy production is greatly affected by the pathology. Result of long standing Ca2+ plateau is destabilisation of the secretory granules and premature activation of the digestive enzymes leading to necrotic cell death. Main attempts so far to break the vicious circle of cell death have been concentrated on reduction of Ca2+ overload or reduction of ATP depletion. This review will summarise these approaches, including recent developments of potential therapies for AP.

Emodin Alleviates Sodium Taurocholate-Induced Pancreatic Ductal Cell Damage by Inhibiting the S100A9/VNN1 Signaling Pathway

OBJECTIVES

Because the pathogenesis of the disease is unclear, the treatment of patients with acute pancreatitis, especially severe acute pancreatitis, is still a major challenge for clinicians. Emodin is an anthraquinone compound extracted from rhubarb that can alleviate the damage to pancreatic ductal epithelial cells induced by adenosine triphosphate, but whether it has a similar protective effect on sodium taurocholate (STC)-stimulated pancreatic ductal cells and the underlying mechanism has not yet been reported.

METHODS

A model of STC-induced HPDE6-C7 human pancreatic ductal epithelial cell injury was established, and then apoptosis and the levels of reactive oxygen species (ROS), glutathione, gamma-glutamylcysteine synthetase, and inflammatory cytokines were assessed in the presence or absence of emodin pretreatment. S100 calcium binding protein A9 (S100A9) and Vanin1 (VNN1) protein expression was also measured.

RESULTS

Emodin significantly increased HPDE6-C7 cell viability, inhibited apoptosis and ROS release, and elevated glutathione levels and gamma-glutamylcysteine synthetase activity. Furthermore, emodin downregulated S100A9 and VNN1 protein expression and inhibited the production of inflammatory factors, such as interleukin (IL)-1β, IL-6, IL-8, and IL-18.

CONCLUSIONS

Emodin attenuates STC-induced pancreatic ductal cell injury possibly by inhibiting S100A9/VNN1-mediated ROS release. This finding provides evidence for the future development of emodin as a therapeutic agent.

FREQUENCY AND SEVERITY OF LIVER INVOLVEMENT IN HYPERTENSIVE DISORDERS OF PREGNANCY

BACKGROUND

Pre-eclampsia (PE) and eclampsia (E) are among the leading causes of maternal and fetal morbidity and mortality. Both are associated with an evolving spectrum of liver disorders.

OBJECTIVE

The aim of this study was to evaluate the frequency and severity of liver involvement in pregnant women admitted to an intensive care unit with PE/E and to assess its influence on adverse maternal and fetal outcomes.

METHODS

All subjects, hospitalized between January 2012 and March 2019, were retrospectively evaluated for clinical and biochemical liver-related abnormalities and their frequencies were subsequently correlated with maternal-fetal outcomes.

RESULTS

A total of 210 women (mean age 31±6.4 years, mean gestational age 33.8±4.1 weeks) with PE/E were included in the study. Most of them had severe hypertension (n=184) and symptoms of abdominal pain (48%) and headache (40%). Liver enzymes abnormalities were seen in 49% of the subjects, usually less than five times the upper limit of normal. Subcapsular hemorrhage and spontaneous hepatic rupture were identified in one woman who died. No patient had definitive diagnosis for acute fatty liver of pregnancy, neither acute liver failure. A total of 62% of deliveries occurred before 37 weeks. Fetal mortality was observed in 6 (3%) cases. There was no correlation between mean levels of liver enzymes and maternal and fetal outcomes.

CONCLUSION

Biochemical abnormalities of liver enzymes are frequently seen in women with PE/E, but outside the spectrum of HELLP syndrome, they are not associated with adverse maternal and fetal outcomes. Liver-related complications are rare but can be life-threatening.

Impaired regulation of PMCA activity by defective CFTR expression promotes epithelial cell damage in alcoholic pancreatitis and hepatitis

Alcoholic pancreatitis and hepatitis are frequent, potentially lethal diseases with limited treatment options. Our previous study reported that the expression of CFTR Cl- channel is impaired by ethanol in pancreatic ductal cells leading to more severe alcohol-induced pancreatitis. In addition to determining epithelial ion secretion, CFTR has multiple interactions with other proteins, which may influence intracellular Ca2+ signaling. Thus, we aimed to investigate the impact of ethanol-mediated CFTR damage on intracellular Ca2+ homeostasis in pancreatic ductal epithelial cells and cholangiocytes. Human and mouse pancreas and liver samples and organoids were used to study ion secretion, intracellular signaling, protein expression and interaction. The effect of PMCA4 inhibition was analyzed in a mouse model of alcohol-induced pancreatitis. The decreased CFTR expression impaired PMCA function and resulted in sustained intracellular Ca2+ elevation in ethanol-treated and mouse and human pancreatic organoids. Liver samples derived from alcoholic hepatitis patients and ethanol-treated mouse liver organoids showed decreased CFTR expression and function, and impaired PMCA4 activity. PMCA4 co-localizes and physically interacts with CFTR on the apical membrane of polarized epithelial cells, where CFTR-dependent calmodulin recruitment determines PMCA4 activity. The sustained intracellular Ca2+ elevation in the absence of CFTR inhibited mitochondrial function and was accompanied with increased apoptosis in pancreatic epithelial cells and PMCA4 inhibition increased the severity of alcohol-induced AP in mice. Our results suggest that improving Ca2+ extrusion in epithelial cells may be a potential novel therapeutic approach to protect the exocrine pancreatic function in alcoholic pancreatitis and prevent the development of cholestasis in alcoholic hepatitis.

Bile acid- and ethanol-mediated activation of Orai1 damages pancreatic ductal secretion in acute pancreatitis

KEY POINTS

Sustained intracellular Ca²⁺ overload in pancreatic acinar and ductal cells is a hallmark of biliary and alcohol-induced acute pancreatitis, which leads to impaired ductal ion and fluid secretion. Orai1 is a plasma membrane Ca²⁺ channel that mediates extracellular Ca²⁺ influx upon endoplasmic reticulum Ca²⁺ depletion. Our results showed that Orai1 is expressed on the luminal plasma membrane of the ductal cells and selective Orai1 inhibition impaired Stim1-dependent extracellular Ca²⁺ influx evoked by bile acids or ethanol combined with non-oxidative ethanol metabolites. The prevention of sustained extracellular Ca²⁺ influx protected ductal cell secretory functions in in vitro models and maintained exocrine pancreatic secretion in in vivo AP models. Orai1 inhibition prevents the bile acid-, and alcohol-induced damage of the pancreatic ductal secretion and holds the potential of improving the outcome of acute pancreatitis.

ABSTRACT

Regardless of its etiology, sustained intracellular Ca²⁺ overload is a well-known hallmark of acute pancreatitis (AP). Toxic Ca²⁺ elevation induces pancreatic ductal cell damage characterized by impaired ion- and fluid secretion -essential to wash out the protein-rich fluid secreted by acinar cells while maintaining the alkaline intra-ductal pH under physiological conditions- and mitochondrial dysfunction. While prevention of ductal cell injury decreases the severity of AP, no specific drug target has yet been identified in the ductal cells. Although Orai1 -a store operated Ca²⁺ influx channel- is known to contribute to sustained Ca²⁺ overload in acinar cells, details concerning its expression and function in ductal cells are currently lacking. In this study, we demonstrate that functionally active Orai1 channels reside dominantly in the apical plasma membrane of pancreatic ductal cells. Selective CM5480-mediated Orai1 inhibition impairs Stim1-dependent extracellular Ca²⁺ influx evoked by bile acids or ethanol combined with non-oxidative ethanol metabolites. Furthermore, prevention of sustained extracellular Ca²⁺ influx protects ductal cell secretory function in vitro and decrease pancreatic ductal cell death. Finally, Orai1-inhibition partially restores and maintains proper exocrine pancreatic secretion in in vivo AP models. In conclusion, our results indicate that Orai1 inhibition prevents AP-related ductal cell function impairment and holds the potential of improving disease outcome. Abstract figure legend  This article is protected by copyright. All rights reserved.

Bicarbonate Transport in Cystic Fibrosis and Pancreatitis

CFTR, the cystic fibrosis (CF) gene-encoded epithelial anion channel, has a prominent role in driving chloride, bicarbonate and fluid secretion in the ductal cells of the exocrine pancreas. Whereas severe mutations in CFTR cause fibrosis of the pancreas in utero, CFTR mutants with residual function, or CFTR variants with a normal chloride but defective bicarbonate permeability (CFTR^BD), are associated with an enhanced risk of pancreatitis. Recent studies indicate that CFTR function is not only compromised in genetic but also in selected patients with an acquired form of pancreatitis induced by alcohol, bile salts or smoking. In this review, we summarize recent insights into the mechanism and regulation of CFTR-mediated and modulated bicarbonate secretion in the pancreatic duct, including the role of the osmotic stress/chloride sensor WNK1 and the scaffolding protein IRBIT, and current knowledge about the role of CFTR in genetic and acquired forms of pancreatitis. Furthermore, we discuss the perspectives for CFTR modulator therapy in the treatment of exocrine pancreatic insufficiency and pancreatitis and introduce pancreatic organoids as a promising model system to study CFTR function in the human pancreas, its role in the pathology of pancreatitis and its sensitivity to CFTR modulators on a personalized basis.

Mislocalization of CFTR expression in acute pancreatitis and the beneficial effect of VX-661 + VX-770 treatment on disease severity

Cystic fibrosis transmembrane conductance regulator (CFTR) has an essential role in maintaining pancreatic ductal function. Impaired CFTR function can trigger acute pancreatitis (AP) and exacerbate disease severity. We aimed to investigate the localization and expression of CFTR during AP, and determined the effects of a CFTR corrector (VX-661) and potentiator (VX-770) on disease severity. AP was induced in FVB/n mice by 6-10 hourly intraperitoneal injections of 50 μg/kg cerulein. Some mice were pre-treated with five to six daily injections of 2 mg/kg VX-661 + VX-770. Control animals were administered physiological saline instead of cerulein and dimethyl sulfoxide instead of VX compounds. AP severity was determined by measuring laboratory and histological parameters; CFTR and CK19 expression was measured. Activity of ion transporters was followed by intracellular pH or fluid secretion measurement of isolated pancreatic intra-/interlobular ducts. Cerulein-induced AP severity was greatest between 12 and 24 h. CFTR mRNA expression was significantly increased 24 h after AP induction. Immunohistochemistry demonstrated disturbed staining morphology of CFTR and CK19 proteins in AP. Mislocalization of CFTR protein was observed from 6 h, while expression increased at 24 h compared to control. Ductal HCO₃ ^- transport activity was significantly increased 6 h after AP induction. AP mice pre-treatment with VX-661 + VX-770 significantly reduced the extent of tissue damage by about 20-30%, but other parameters were unchanged. Interestingly, VX-661 + VX-770 in vitro administration significantly increased the fluid secretion of ducts derived from AP animals. This study described the course of the CFTR expression and mislocalization in cerulein-induced AP. Our results suggest that the beneficial effects of CFTR correctors and potentiators should be further investigated in AP. KEY POINTS: Cystic fibrosis transmembrane conductance regulator (CFTR) is an important ion channel in epithelial cells. Its malfunction has several serious consequences, like developing or aggravating acute pancreatitis (AP). Here, the localization and expression of CFTR during cerulein-induced AP in mice were investigated and the effects of CFTR corrector (VX-661) and a potentiator (VX-770) on disease severity were determined. CFTR mRNA expression was significantly increased and mislocalization of CFTR protein was observed in AP compared to the control group. Interestingly, pre-treatment of AP mice with VX-661 + VX-770 significantly reduced the extent of pancreatic tissue damage by 20-30%. In vitro administration of VX-661 + VX-770 significantly increased the fluid secretion of ducts derived from AP animals. Based on these results, the utilization of CFTR correctors and potentiators should be further investigated in AP.

The roles of calcium and ATP in the physiology and pathology of the exocrine pancreas

This review deals with the roles of calcium ions and ATP in the control of the normal functions of the different cell types in the exocrine pancreas as well as the roles of these molecules in the pathophysiology of acute pancreatitis. Repetitive rises in the local cytosolic calcium ion concentration in the apical part of the acinar cells not only activate exocytosis but also, via an increase in the intramitochondrial calcium ion concentration, stimulate the ATP formation that is needed to fuel the energy-requiring secretion process. However, intracellular calcium overload, resulting in a global sustained elevation of the cytosolic calcium ion concentration, has the opposite effect of decreasing mitochondrial ATP production, and this initiates processes that lead to necrosis. In the last few years it has become possible to image calcium signaling events simultaneously in acinar, stellate, and immune cells in intact lobules of the exocrine pancreas. This has disclosed processes by which these cells interact with each other, particularly in relation to the initiation and development of acute pancreatitis. By unraveling the molecular mechanisms underlying this disease, several promising therapeutic intervention sites have been identified. This provides hope that we may soon be able to effectively treat this often fatal disease.

The Role of Mitochondria in the Chemoresistance of Pancreatic Cancer Cells

The first-line chemotherapies for patients with unresectable pancreatic cancer (PC) are 5-fluorouracil (5-FU) and gemcitabine therapy. However, due to chemoresistance the prognosis of patients with PC has not been significantly improved. Mitochondria are essential organelles in eukaryotes that evolved from aerobic bacteria. In recent years, many studies have shown that mitochondria play important roles in tumorigenesis and may act as chemotherapeutic targets in PC. In addition, according to recent studies, mitochondria may play important roles in the chemoresistance of PC by affecting apoptosis, metabolism, mtDNA metabolism, and mitochondrial dynamics. Interfering with some of these factors in mitochondria may improve the sensitivity of PC cells to chemotherapeutic agents, such as gemcitabine, making mitochondria promising targets for overcoming chemoresistance in PC.

Role of Bile Acids and Bile Salts in Acute Pancreatitis: From the Experimental to Clinical Studies

ABSTRACT

Acute pancreatitis (AP) is one of the most common gastroenterological disorders leading to hospitalization. It has long been debated whether biliary AP, about 30% to 50% of all cases, is induced by bile acids (BAs) when they reach the pancreas via reflux or via the systemic blood circulation.Besides their classical function in digestion, BAs have become an attractive research target because of their recently discovered property as signaling molecules. The underlying mechanisms of BAs have been investigated in various studies. Bile acids are internalized into acinar cells through specific G-protein-coupled BA receptor 1 and various transporters. They can further act via different receptors: the farnesoid X, ryanodine, and inositol triphosphate receptor. Bile acids induce a sustained Ca2+ influx from the endoplasmic reticulum and release of Ca2+ from acidic stores into the cytosol of acinar cells. The overload of intracellular Ca2+ results in mitochondrial depolarization and subsequent acinar cell necrosis. In addition, BAs have a biphasic effect on pancreatic ductal cells. A more detailed characterization of the mechanisms through which BAs contribute to the disease pathogenesis and severity will greatly improve our understanding of the underlying pathophysiology and may allow for the development of therapeutic and preventive strategies for gallstone-inducedAP.

Intracellular Ca2+ Signalling in the Pathogenesis of Acute Pancreatitis: Recent Advances and Translational Perspectives

Intracellular Ca²⁺ signalling is a major signal transductional pathway in non-excitable cells, responsible for the regulation of a variety of physiological functions. In the secretory epithelial cells of the exocrine pancreas, such as acinar and ductal cells, intracellular Ca²⁺ elevation regulates digestive enzyme secretion in acini or fluid and ion secretion in ductal cells. Although Ca²⁺ is a uniquely versatile orchestrator of epithelial physiology, unregulated global elevation of the intracellular Ca²⁺ concentration is an early trigger for the development of acute pancreatitis (AP). Regardless of the aetiology, different forms of AP all exhibit sustained intracellular Ca²⁺ elevation as a common hallmark. The release of endoplasmic reticulum (ER) Ca²⁺ stores by toxins (such as bile acids or fatty acid ethyl esters (FAEEs)) or increased intrapancreatic pressure activates the influx of extracellular Ca²⁺ via the Orai1 Ca²⁺ channel, a process known as store-operated Ca²⁺ entry (SOCE). Intracellular Ca²⁺ overload can lead to premature activation of trypsinogen in pancreatic acinar cells and impaired fluid and HCO₃^- secretion in ductal cells. Increased and unbalanced reactive oxygen species (ROS) production caused by sustained Ca²⁺ elevation further contributes to cell dysfunction, leading to mitochondrial damage and cell death. Translational studies of AP identified several potential target molecules that can be modified to prevent intracellular Ca²⁺ overload. One of the most promising drugs, a selective inhibitor of the Orai1 channel that has been shown to inhibit extracellular Ca²⁺ influx and protect cells from injury, is currently being tested in clinical trials. In this review, we will summarise the recent advances in the field, with a special focus on the translational aspects of the basic findings.

TRPM2-mediated extracellular Ca2+ entry promotes acinar cell necrosis in biliary acute pancreatitis

KEY POINTS

Acute biliary pancreatitis is a significant clinical challenge as currently no specific pharmaceutical treatment exists. Intracellular Ca²⁺ overload, increased reactive oxygen species (ROS) production, mitochondrial damage and intra-acinar digestive enzyme activation caused by bile acids are hallmarks of acute biliary pancreatitis. Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that has recently emerged as an important contributor to oxidative-stress-induced cellular Ca²⁺ overload across different diseases. We demonstrated that TRPM2 is expressed in the plasma membrane of mouse pancreatic acinar and ductal cells, which can be activated by increased oxidative stress induced by H₂ O₂ treatment and contributed to bile acid-induced extracellular Ca²⁺ influx in acinar cells, which promoted acinar cell necrosis in vitro and in vivo. These results suggest that the inhibition of TRPM2 may be a potential treatment option for biliary pancreatitis.

ABSTRACT

Acute biliary pancreatitis poses a significant clinical challenge as currently no specific pharmaceutical treatment exists. Disturbed intracellular Ca²⁺ signalling caused by bile acids is a hallmark of the disease, which induces increased reactive oxygen species (ROS) production, mitochondrial damage, intra-acinar digestive enzyme activation and cell death. Because of this mechanism of action, prevention of toxic cellular Ca²⁺ overload is a promising therapeutic target. Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that has recently emerged as an important contributor to oxidative-stress-induced cellular Ca²⁺ overload across different diseases. However, the expression and possible functions of TRPM2 in the exocrine pancreas remain unknown. Here we found that TRPM2 is expressed in the plasma membrane of mouse pancreatic acinar and ductal cells, which can be activated by increased oxidative stress induced by H₂ O₂ treatment. TRPM2 activity was found to contribute to bile acid-induced extracellular Ca²⁺ influx in acinar cells, but did not have the same effect in ductal cells. The generation of intracellular ROS in response to bile acids was remarkably higher in pancreatic acinar cells compared to isolated ducts, which can explain the difference between acinar and ductal cells. This activity promoted acinar cell necrosis in vitro independently from mitochondrial damage or mitochondrial fragmentation. In addition, bile-acid-induced experimental pancreatitis was less severe in TRPM2 knockout mice, whereas the lack of TRPM2 had no protective effect in cerulein-induced acute pancreatitis. Our results suggest that the inhibition of TRPM2 may be a potential treatment option for biliary pancreatitis.

Mouse pancreatic ductal organoid culture as a relevant model to study exocrine pancreatic ion secretion

Pancreatic exocrine secretory processes are challenging to investigate on primary epithelial cells. Pancreatic organoid cultures may help to overcome shortcomings of the current models, however the ion secretory processes in pancreatic organoids-and therefore their physiological relevance or their utility in disease modeling-are not known. To answer these questions, we provide side-by-side comparison of gene expression, morphology, and function of epithelial cells in primary isolated pancreatic ducts and organoids. We used mouse pancreatic ductal fragments for experiments or were grown in Matrigel to obtain organoid cultures. Using PCR analysis we showed that gene expression of ion channels and transporters remarkably overlap in primary ductal cells and organoids. Morphological analysis with scanning electron microscopy revealed that pancreatic organoids form polarized monolayers with brush border on the apical membrane. Whereas the expression and localization of key proteins involved in ductal secretion (cystic fibrosis transmembrane conductance regulator, Na⁺/H⁺ exchanger 1 and electrogenic Na⁺/HCO₃^- cotransporter 1) are equivalent to the primary ductal fragments. Measurements of intracellular pH and Cl^- levels revealed no significant difference in the activities of the apical Cl^-/HCO₃^- exchange, or in the basolateral Na⁺ dependent HCO₃^- uptake. In summary we found that ion transport activities in the mouse pancreatic organoids are remarkably similar to those observed in freshly isolated primary ductal fragments. These results suggest that organoids can be suitable and robust model to study pancreatic ductal epithelial ion transport in health and diseases and facilitate drug development for secretory pancreatic disorders like cystic fibrosis, or chronic pancreatitis.

Novel mitochondrial transition pore inhibitor N-methyl-4-isoleucine cyclosporin is a new therapeutic option in acute pancreatitis

KEY POINTS

•Bile acids, ethanol and fatty acids affect pancreatic ductal fluid and bicarbonate secretion via mitochondrial damage, ATP depletion and calcium overload. •Pancreatitis-inducing factors open the membrane transition pore (mPTP) channel via cyclophilin D activation in acinar cells, causing calcium overload and cell death; genetic or pharmacological inhibition of mPTP improves the outcome of acute pancreatitis in animal models. •Here we show that genetic and pharmacological inhibition of mPTP protects mitochondrial homeostasis and cell function evoked by pancreatitis-inducing factors in pancreatic ductal cells. •The results also show that the novel cyclosporin A derivative NIM811 protects mitochondrial function in acinar and ductal cells, and it preserves bicarbonate transport mechanisms in pancreatic ductal cells. •We found that NIM811 is highly effective in different experimental pancreatitis models and has no side-effects. NIM811 is a highly suitable compound to be tested in clinical trials.

ABSTRACT

Mitochondrial dysfunction plays a crucial role in the development of acute pancreatitis (AP); however, no compound is currently available with clinically acceptable effectiveness and safety. In this study, we investigated the effects of a novel mitochondrial transition pore inhibitor, N-methyl-4-isoleucine cyclosporin (NIM811), in AP. Pancreatic ductal and acinar cells were isolated by enzymatic digestion from Bl/6 mice. In vitro measurements were performed by confocal microscopy and microfluorometry. Preventative effects of pharmacological [cylosporin A (2 µm), NIM811 (2 µm)] or genetic (Ppif^-/- /Cyp D KO) inhibition of the mitochondrial transition pore (mPTP) during the administration of either bile acids (BA) or ethanol + fatty acids (EtOH+FA) were examined. Toxicity of mPTP inhibition was investigated by detecting apoptosis and necrosis. In vivo effects of the most promising compound, NIM811 (5 or 10 mg kg^-1 per os), were checked in three different AP models induced by either caerulein (10 × 50 µg kg^-1 ), EtOH+FA (1.75 g kg^-1 ethanol and 750 mg kg^-1 palmitic acid) or 4% taurocholic acid (2 ml kg^-1 ). Both genetic and pharmacological inhibition of Cyp D significantly prevented the toxic effects of BA and EtOH+FA by restoring mitochondrial membrane potential (Δψ) and preventing the loss of mitochondrial mass. In vivo experiments revealed that per os administration of NIM811 has a protective effect in AP by reducing oedema, necrosis, leukocyte infiltration and serum amylase level in AP models. Administration of NIM811 had no toxic effects. The novel mitochondrial transition pore inhibitor NIM811 thus seems to be an exceptionally good candidate compound for clinical trials in AP.

New insights into acute pancreatitis

The incidence of acute pancreatitis continues to increase worldwide, and it is one of the most common gastrointestinal causes for hospital admission in the USA. In the past decade, substantial advancements have been made in our understanding of the pathophysiological mechanisms of acute pancreatitis. Studies have elucidated mechanisms of calcium-mediated acinar cell injury and death and the importance of store-operated calcium entry channels and mitochondrial permeability transition pores. The cytoprotective role of the unfolded protein response and autophagy in preventing sustained endoplasmic reticulum stress, apoptosis and necrosis has also been characterized, as has the central role of unsaturated fatty acids in causing pancreatic organ failure. Characterization of these pathways has led to the identification of potential molecular targets for future therapeutic trials. At the patient level, two classification systems have been developed to classify the severity of acute pancreatitis into prognostically meaningful groups, and several landmark clinical trials have informed management strategies in areas of nutritional support and interventions for infected pancreatic necrosis that have resulted in important changes to acute pancreatitis management paradigms. In this Review, we provide a summary of recent advances in acute pancreatitis with a special emphasis on pathophysiological mechanisms and clinical management of the disorder.

Hypoxia-Inducible Factor-1α Knockdown Plus Glutamine Supplementation Attenuates the Predominance of Necrosis over Apoptosis by Relieving Cellular Energy Stress in Acute Pancreatitis

The present study was conducted to investigate the effect and potential mechanism of hypoxia-inducible factor-1α (HIF-1α) genetic inhibition plus glutamine (Gln) supplementation on necrosis-apoptosis imbalance during acute pancreatitis (AP), with a specific focus on the regulations of intracellular energy metabolism status. Wistar rats and AR42J cells were used to establish AP models. When indicated, a HIF-1α knockdown with or without a Gln supplementation was administered. In vivo, local and systemic inflammatory injuries were assessed by serum cytokine measurement, H&E staining, and transmission electron microscope (TEM) observation of pancreatic tissue. In vitro, intracellular energy metabolism status was evaluated by measuring the intracellular adenosine triphosphate (ATP), lactic acid, and Ca²⁺ concentrations and the mitochondrial potential. In addition, changes in the apoptotic activity were analyzed using TUNEL staining in vivo and an apoptosis assay in vitro. HIF-1α knockdown alleviated AP-related inflammatory injury as indicated by the measurements of serum cytokines and examinations of TEM and H&E staining of pancreatic tissues. HIF-1α knockdown played an antioxidative role against AP-related injuries by preventing the increase in the intracellular Ca²⁺ concentration and the decrease in the mitochondrial membrane potential and subsequently by suppressing the glycolysis pathway and increasing energy anabolism in AR42J cells after AP induction. Apoptosis was significantly upregulated when HIF-1α was knocked down before AP induction due to an attenuation of the translocation of nuclear factor-kappa B to the nuclei. Furthermore, these merits of HIF-1α knockdown in the relief of the metabolic stress and upregulation of apoptosis were more significant when Gln was administered concomitantly. In conclusion, Gln-supplemented HIF-1α knockdown might be promising for the future management of AP by relieving the intracellular energy stress, thereby attenuating the predominance of necrosis over apoptosis.

Guts and Gall: Bile Acids in Regulation of Intestinal Epithelial Function in Health and Disease

Epithelial cells line the entire surface of the gastrointestinal tract and its accessory organs where they primarily function in transporting digestive enzymes, nutrients, electrolytes, and fluid to and from the luminal contents. At the same time, epithelial cells are responsible for forming a physical and biochemical barrier that prevents the entry into the body of harmful agents, such as bacteria and their toxins. Dysregulation of epithelial transport and barrier function is associated with the pathogenesis of a number of conditions throughout the intestine, such as inflammatory bowel disease, chronic diarrhea, pancreatitis, reflux esophagitis, and cancer. Driven by discovery of specific receptors on intestinal epithelial cells, new insights into mechanisms that control their synthesis and enterohepatic circulation, and a growing appreciation of their roles as bioactive bacterial metabolites, bile acids are currently receiving a great deal of interest as critical regulators of epithelial function in health and disease. This review aims to summarize recent advances in this field and to highlight how bile acids are now emerging as exciting new targets for disease intervention.

Cystic Fibrosis of the Pancreas: The Role of CFTR Channel in the Regulation of Intracellular Ca2+ Signaling and Mitochondrial Function in the Exocrine Pancreas

Cystic fibrosis (CF) is the most common genetic disorder that causes a significant damage in secretory epithelial cells due to the defective ion flux across the cystic fibrosis transmembrane conductance regulator (CFTR) Cl^- channel. Pancreas is one of the organs most frequently damaged by the disease leading to pancreatic insufficiency, abdominal pain and an increased risk of acute pancreatitis in CF patients causing a significant decrease in the quality of life. CFTR plays a central role in the pancreatic ductal secretory functions by carrying Cl^- and HCO₃ ^- ions across the apical membrane. Therefore pathophysiological studies in CF mostly focused on the effects of impaired ion secretion by pancreatic ductal epithelial cells leading to exocrine pancreatic damage. However, several studies indicated that CFTR has a central role in the regulation of intracellular signaling processes and is now more widely considered as a signaling hub in epithelial cells. In contrast, elevated intracellular Ca²⁺ level was observed in the lack of functional CFTR in different cell types including airway epithelial cells. In addition, impaired CFTR expression has been correlated with damaged mitochondrial function in epithelial cells. These alterations of intracellular signaling in CF are not well characterized in the exocrine pancreas yet. Therefore in this review we would like to summarize the complex role of CFTR in the exocrine pancreas with a special focus on the intracellular signaling and mitochondrial function.

F1F0-ATP Synthase Inhibitory Factor 1 in the Normal Pancreas and in Pancreatic Ductal Adenocarcinoma: Effects on Bioenergetics, Invasion and Proliferation

F1F0-ATP synthase inhibitory factor 1 (IF1) inhibits the reverse mode of F1F0-ATP synthase, and therefore protects cellular ATP content at the expense of accelerated loss of mitochondrial membrane potential (ΔΨm). There is considerable variability in IF1 expression and its influence on bioenergetics between different cell types. High levels of IF1 in a number of cancers have been linked to increased glycolysis, resistance to cell death, increased migration and proliferation. However, neither the expression nor role of IF1 in the normal pancreas or in pancreatic cancer has been characterized. In this study, we found that pancreatic ductal adenocarcinoma (PDAC) patients express higher levels of IF1 in cancerous cells than in pancreatic acinar cells (PACs). PDAC cell lines have a higher IF1 content and IF1/ATP synthase ratio than PACs. The observed differences are consistent with the ability of the respective cell types to maintain ΔΨm and ATP levels in conditions of chemical hypoxia. Acinar cells and PDAC cells preferentially express different IF1 isoforms. Both knockdown and knockout of IF1 in the PANC-1 pancreatic cancer cell line modified cellular bioenergetics and decreased migration, invasion and proliferation suggesting the putative importance of IF1 for PDAC growth and metastasis.

Ca2+ toxicity and mitochondrial damage in acute pancreatitis: translational overview

Acute pancreatitis (AP) is a leading cause of hospitalization among non-malignant gastrointestinal disorders. The mortality of severe AP can reach 30-50%, which is most probably owing to the lack of specific treatment. Therefore, AP is a major healthcare problem, which urges researchers to identify novel drug targets. Studies from the last decades highlighted that the toxic cellular Ca(2+) overload and mitochondrial damage are key pathogenic steps in the disease development affecting both acinar and ductal cell functions. Moreover, recent observations showed that modifying the cellular Ca(2+) signalling might be beneficial in AP. The inhibition of Ca(2+) release from the endoplasmic reticulum or the activity of plasma membrane Ca(2+) influx channels decreased the severity of AP in experimental models. Similarly, inhibition of mitochondrial permeability transition pore (MPTP) opening also seems to improve the outcome of AP in in vivo animal models. At the moment MPTP blockers are under detailed clinical investigation to test whether interventions in MPTP openings and/or Ca(2+) homeostasis of the cells can be specific targets in prevention or treatment of cell damage in AP.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'.

Bile acids induce necrosis in pancreatic stellate cells dependent on calcium entry and sodium-driven bile uptake

KEY POINTS

Acute biliary pancreatitis is a sudden and severe condition initiated by bile reflux into the pancreas. Bile acids are known to induce Ca2+ signals and necrosis in isolated pancreatic acinar cells but the effects of bile acids on stellate cells are unexplored. Here we show that cholate and taurocholate elicit more dramatic Ca2+ signals and necrosis in stellate cells compared to the adjacent acinar cells in pancreatic lobules; whereas taurolithocholic acid 3-sulfate primarily affects acinar cells. Ca2+ signals and necrosis are strongly dependent on extracellular Ca2+ as well as Na+ ; and Na+ -dependent transport plays an important role in the overall bile acid uptake in pancreatic stellate cells. Bile acid-mediated pancreatic damage can be further escalated by bradykinin-induced signals in stellate cells and thus killing of stellate cells by bile acids might have important implications in acute biliary pancreatitis.

ABSTRACT

Acute biliary pancreatitis, caused by bile reflux into the pancreas, is a serious condition characterised by premature activation of digestive enzymes within acinar cells, followed by necrosis and inflammation. Bile acids are known to induce pathological Ca2+ signals and necrosis in acinar cells. However, bile acid-elicited signalling events in stellate cells remain unexplored. This is the first study to demonstrate the pathophysiological effects of bile acids on stellate cells in two experimental models: ex vivo (mouse pancreatic lobules) and in vitro (human cells). Sodium cholate and taurocholate induced cytosolic Ca2+ elevations in stellate cells, larger than those elicited simultaneously in the neighbouring acinar cells. In contrast, taurolithocholic acid 3-sulfate (TLC-S), known to induce Ca2+ oscillations in acinar cells, had only minor effects on stellate cells in lobules. The dependence of the Ca2+ signals on extracellular Na+ and the presence of sodium-taurocholate cotransporting polypeptide (NTCP) indicate a Na+ -dependent bile acid uptake mechanism in stellate cells. Bile acid treatment caused necrosis predominantly in stellate cells, which was abolished by removal of extracellular Ca2+ and significantly reduced in the absence of Na+ , showing that bile-dependent cell death was a downstream event of Ca2+ signals. Finally, combined application of TLC-S and the inflammatory mediator bradykinin caused more extensive necrosis in both stellate and acinar cells than TLC-S alone. Our findings shed new light on the mechanism by which bile acids promote pancreatic pathology. This involves not only signalling in acinar cells but also in stellate cells.

Meta-Analysis of Early Nutrition: The Benefits of Enteral Feeding Compared to a Nil Per Os Diet Not Only in Severe, but Also in Mild and Moderate Acute Pancreatitis

The recently published guidelines for acute pancreatitis (AP) suggest that enteral nutrition (EN) should be the primary therapy in patients suffering from severe acute pancreatitis (SAP); however, none of the guidelines have recommendations on mild and moderate AP (MAP). A meta-analysis was performed using the preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P). The following PICO (problem, intervention, comparison, outcome) was applied: P: nutrition in AP; I: enteral nutrition (EN); C: nil per os diet (NPO); and O: outcome. There were 717 articles found in Embase, 831 in PubMed, and 10 in the Cochrane database. Altogether, seven SAP and six MAP articles were suitable for analyses. In SAP, forest plots were used to illustrate three primary endpoints (mortality, multiorgan failure, and intervention). In MAP, 14 additional secondary endpoints were analyzed (such as CRP (C-reactive protein), WCC (white cell count), complications, etc.). After pooling the data, the Mann-Whitney U test was used to detect significant differences. Funnel plots were created for testing heterogeneity. All of the primary endpoints investigated showed that EN is beneficial vs. NPO in SAP. In MAP, all of the six articles found merit in EN. Analyses of the primary endpoints did not show significant differences between the groups; however, analyzing the 17 endpoints together showed a significant difference in favor of EN vs. NPO. EN is beneficial compared to a nil per os diet not only in severe, but also in mild and moderate AP.

Role of CFTR in epithelial physiology

Salt and fluid absorption and secretion are two processes that are fundamental to epithelial function and whole body fluid homeostasis, and as such are tightly regulated in epithelial tissues. The CFTR anion channel plays a major role in regulating both secretion and absorption in a diverse range of epithelial tissues, including the airways, the GI and reproductive tracts, sweat and salivary glands. It is not surprising then that defects in CFTR function are linked to disease, including life-threatening secretory diarrhoeas, such as cholera, as well as the inherited disease, cystic fibrosis (CF), one of the most common life-limiting genetic diseases in Caucasian populations. More recently, CFTR dysfunction has also been implicated in the pathogenesis of acute pancreatitis, chronic obstructive pulmonary disease (COPD), and the hyper-responsiveness in asthma, underscoring its fundamental role in whole body health and disease. CFTR regulates many mechanisms in epithelial physiology, such as maintaining epithelial surface hydration and regulating luminal pH. Indeed, recent studies have identified luminal pH as an important arbiter of epithelial barrier function and innate defence, particularly in the airways and GI tract. In this chapter, we will illustrate the different operational roles of CFTR in epithelial function by describing its characteristics in three different tissues: the airways, the pancreas, and the sweat gland.

Epithelial Anion Transport as Modulator of Chemokine Signaling

The pivotal role of epithelial cells is to secrete and absorb ions and water in order to allow the formation of a luminal fluid compartment that is fundamental for the epithelial function as a barrier against environmental factors. Importantly, epithelial cells also take part in the innate immune system. As a first line of defense they detect pathogens and react by secreting and responding to chemokines and cytokines, thus aggravating immune responses or resolving inflammatory states. Loss of epithelial anion transport is well documented in a variety of diseases including cystic fibrosis, chronic obstructive pulmonary disease, asthma, pancreatitis, and cholestatic liver disease. Here we review the effect of aberrant anion secretion with focus on the release of inflammatory mediators by epithelial cells and discuss putative mechanisms linking these transport defects to the augmented epithelial release of chemokines and cytokines. These mechanisms may contribute to the excessive and persistent inflammation in many respiratory and gastrointestinal diseases.

A novel, protective role of ursodeoxycholate in bile-induced pancreatic ductal injury

We have previously shown that chenodeoxycholic acid (CDCA) strongly inhibits pancreatic ductal HCO3 (-) secretion through the destruction of mitochondrial function, which may have significance in the pathomechanism of acute pancreatitis (AP). Ursodeoxycholic acid (UDCA) is known to protect the mitochondria against hydrophobic bile acids and has an ameliorating effect on cell death. Therefore, our aim was to investigate the effect of UDCA pretreatment on CDCA-induced pancreatic ductal injury. Guinea pig intrainterlobular pancreatic ducts were isolated by collagenase digestion. Ducts were treated with UDCA for 5 and 24 h, and the effect of CDCA on intracellular Ca(2+) concentration ([Ca(2+)]i), intracellular pH (pHi), morphological and functional changes of mitochondria, and the rate of apoptosis were investigated. AP was induced in rat by retrograde intraductal injection of CDCA (0.5%), and the disease severity of pancreatitis was assessed by measuring standard laboratory and histological parameters. Twenty-four-hour pretreatment of pancreatic ducts with 0.5 mM UDCA significantly reduced the rate of ATP depletion, mitochondrial injury, and cell death induced by 1 mM CDCA and completely prevented the inhibitory effect of CDCA on acid-base transporters. UDCA pretreatment had no effect on CDCA-induced Ca(2+) signaling. Oral administration of UDCA (250 mg/kg) markedly reduced the severity of CDCA-induced AP. Our results clearly demonstrate that UDCA 1) suppresses the CDCA-induced pancreatic ductal injury by reducing apoptosis and mitochondrial damage and 2) reduces the severity of CDCA-induced AP. The protective effect of UDCA against hydrophobic bile acids may represent a novel therapeutic target in the treatment of biliary AP.

CFTR: A New Horizon in the Pathomechanism and Treatment of Pancreatitis

Cystic fibrosis transmembrane conductance regulator (CFTR) is an ion channel that conducts chloride and bicarbonate ions across epithelial cell membranes. Mutations in the CFTR gene diminish the ion channel function and lead to impaired epithelial fluid transport in multiple organs such as the lung and the pancreas resulting in cystic fibrosis. Heterozygous carriers of CFTR mutations do not develop cystic fibrosis but exhibit increased risk for pancreatitis and associated pancreatic damage characterized by elevated mucus levels, fibrosis, and cyst formation. Importantly, recent studies demonstrated that pancreatitis causing insults, such as alcohol, smoking, or bile acids, strongly inhibit CFTR function. Furthermore, human studies showed reduced levels of CFTR expression and function in all forms of pancreatitis. These findings indicate that impairment of CFTR is critical in the development of pancreatitis; therefore, correcting CFTR function could be the first specific therapy in pancreatitis. In this review, we summarize recent advances in the field and discuss new possibilities for the treatment of pancreatitis.

The Physiology and Pathophysiology of Pancreatic Ductal Secretion: The Background for Clinicians

The human exocrine pancreas consists of 2 main cell types: acinar and ductal cells. These exocrine cells interact closely to contribute to the secretion of pancreatic juice. The most important ion in terms of the pancreatic ductal secretion is HCO3. In fact, duct cells produce an alkaline fluid that may contain up to 140 mM NaHCO3, which is essential for normal digestion. This article provides an overview of the basics of pancreatic ductal physiology and pathophysiology. In the first part of the article, we discuss the ductal electrolyte and fluid transporters and their regulation. The central role of cystic fibrosis transmembrane conductance regulator (CFTR) is highlighted, which is much more than just a Cl channel. We also review the role of pancreatic ducts in severe debilitating diseases such as cystic fibrosis (caused by various genetic defects of cftr), pancreatitis, and diabetes mellitus. Stimulation of ductal secretion in cystic fibrosis and pancreatitis may have beneficial effects in their treatment.

Cystic fibrosis-style changes in the early phase of pancreatitis

The early phase of both acute and chronic pancreatitis can be characterized by disrupt level and function of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, decreased bicarbonate secretion, intraductal acidosis, decrease of fluid secretion and elevation of mucoprotein levels. It is almost needless to say that these intrapancreatic changes are very similar to the pathophysiological changes observed in cystic fibrosis. The aim of this mini review is to describe the development of the above mentioned pathological observations in details, moreover highlight some future therapeutic opportunities in pancreatitis.

Bile acids inhibit Na⁺/H⁺ exchanger and Cl⁻/HCO₃⁻ exchanger activities via cellular energy breakdown and Ca²⁺ overload in human colonic crypts

Bile acids play important physiological role in the solubilisation and absorption of dietary lipids. However, under pathophysiological conditions, such as short bowel syndrome, they can reach the colon in high concentrations inducing diarrhoea. In this study, our aim was to characterise the cellular pathomechanism of bile-induced diarrhoea using human samples. Colonic crypts were isolated from biopsies of patients (controls with negative colonoscopic findings) and of cholecystectomised/ileum-resected patients with or without diarrhoea. In vitro measurement of the transporter activities revealed impaired Na⁺/H⁺ exchanger (NHE) and Cl⁻/HCO₃⁻ exchanger (CBE) activities in cholecystectomised/ileum-resected patients suffering from diarrhoea, compared to control patients. Acute treatment of colonic crypts with 0.3 mM chenodeoxycholate caused dose-dependent intracellular acidosis; moreover, the activities of acid/base transporters (NHE and CBE) were strongly impaired. This concentration of chenodeoxycholate did not cause morphological changes in colonic epithelial cells, although significantly reduced the intracellular ATP level, decreased mitochondrial transmembrane potential and caused sustained intracellular Ca²⁺ elevation. We also showed that chenodeoxycholate induced Ca²⁺ release from the endoplasmic reticulum and extracellular Ca²⁺ influx contributing to the Ca²⁺ elevation. Importantly, our results suggest that the chenodeoxycholate-induced inhibition of NHE activities was ATP-dependent, whereas the inhibition of CBE activity was mediated by the sustained Ca²⁺ elevation. We suggest that bile acids inhibit the function of ion transporters via cellular energy breakdown and Ca²⁺ overload in human colonic epithelial cells, which can reduce fluid and electrolyte absorption in the colon and promote the development of diarrhea.

The role of pancreatic ducts in the pathogenesis of acute pancreatitis

Pancreatic ducts secrete 2.5 l of alkaline, HCO3(-)-rich fluid daily which greatly contributes to the homeostasis of the pancreas. Ducts are also important in the pathophysiology of the pancreas; alteration of ductal function can lead to severe diseases such as cystic fibrosis and chronic pancreatitis. The role of pancreatic ducts in the development of acute pancreatitis has only been uncovered recently. Pancreatitis inducing agents like bile acids and ethanol dose-dependently affect pancreatic ductal secretion; low concentrations stimulate, whereas high concentrations inhibit secretion. The majority of the review will focus on the central role of cystic fibrosis transmembrane conductance regulator (CFTR), a critical protein in the regulation of ductal secretion, in the pathogenesis of acute pancreatitis which is highlighted by numerous investigations. Downregulation of CFTR expression results in increased severity of acute pancreatitis in mice. Furthermore, human genetic studies have demonstrated statistically significant association of CFTR mutations with acute recurrent pancreatitis. Overall, the data support the involvement of pancreatic ducts in the pathogenesis of acute pancreatitis.

Breakdown of bioenergetics evoked by mitochondrial damage in acute pancreatitis: Mechanisms and consequences

Acute pancreatitis is a severe inflammatory disease with unacceptably high mortality and without specific therapy. Clinical studies revealed that energy supplementation of patients via enteral feeding decreases systemic infections, multi-organ failure and mortality. These clinical observations have been supported by in vitro and in vivo experimental studies which showed that the most common pancreatitis inducing factors, such as bile acids, ethanol and non-oxidative ethanol metabolites induce intracellular ATP depletion and mitochondrial damage both in pancreatic acinar and ductal cells. Notably, the in vitro supplementation of ATP prevented the cellular damage and restored cell functions in both cell types. These observations suggest that either prevention of mitochondrial damage or restoration of intracellular ATP level might provide therapeutical benefits.

Alcohol disrupts levels and function of the cystic fibrosis transmembrane conductance regulator to promote development of pancreatitis

BACKGROUND & AIMS

Excessive consumption of ethanol is one of the most common causes of acute and chronic pancreatitis. Alterations to the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) also cause pancreatitis. However, little is known about the role of CFTR in the pathogenesis of alcohol-induced pancreatitis.

METHODS

We measured CFTR activity based on chloride concentrations in sweat from patients with cystic fibrosis, patients admitted to the emergency department because of excessive alcohol consumption, and healthy volunteers. We measured CFTR levels and localization in pancreatic tissues and in patients with acute or chronic pancreatitis induced by alcohol. We studied the effects of ethanol, fatty acids, and fatty acid ethyl esters on secretion of pancreatic fluid and HCO3(-), levels and function of CFTR, and exchange of Cl(-) for HCO3(-) in pancreatic cell lines as well as in tissues from guinea pigs and CFTR knockout mice after administration of alcohol.

RESULTS

Chloride concentrations increased in sweat samples from patients who acutely abused alcohol but not in samples from healthy volunteers, indicating that alcohol affects CFTR function. Pancreatic tissues from patients with acute or chronic pancreatitis had lower levels of CFTR than tissues from healthy volunteers. Alcohol and fatty acids inhibited secretion of fluid and HCO3(-), as well as CFTR activity, in pancreatic ductal epithelial cells. These effects were mediated by sustained increases in concentrations of intracellular calcium and adenosine 3',5'-cyclic monophosphate, depletion of adenosine triphosphate, and depolarization of mitochondrial membranes. In pancreatic cell lines and pancreatic tissues of mice and guinea pigs, administration of ethanol reduced expression of CFTR messenger RNA, reduced the stability of CFTR at the cell surface, and disrupted folding of CFTR at the endoplasmic reticulum. CFTR knockout mice given ethanol or fatty acids developed more severe pancreatitis than mice not given ethanol or fatty acids.

CONCLUSIONS

Based on studies of human, mouse, and guinea pig pancreata, alcohol disrupts expression and localization of the CFTR. This appears to contribute to development of pancreatitis. Strategies to increase CFTR levels or function might be used to treat alcohol-associated pancreatitis.

Potassium channels in pancreatic duct epithelial cells: their role, function and pathophysiological relevance

Pancreatic ductal epithelial cells play a fundamental role in HCO3 (-) secretion, a process which is essential for maintaining the integrity of the pancreas. Although several studies have implicated impaired HCO3 (-) and fluid secretion as a triggering factor in the development of pancreatitis, the mechanism and regulation of HCO3 (-) secretion is still not completely understood. To date, most studies on the ion transporters that orchestrate ductal HCO3 (-) secretion have focussed on the role of Cl(-)/HCO3 (-) exchangers and Cl(-) channels, whereas much less is known about the role of K(+) channels. However, there is growing evidence that many types of K(+) channels are present in ductal cells where they have an essential role in establishing and maintaining the electrochemical driving force for anion secretion. For this reason, strategies that increase K(+) channel function may help to restore impaired HCO3 (-) and fluid secretion, such as in pancreatitis, and therefore provide novel directions for future pancreatic therapy. In this review, our aims are to summarize the types of K(+) channels found in pancreatic ductal cells and to discuss their individual roles in ductal HCO3 (-) secretion. We will also describe how K(+) channels are involved in pathophysiological conditions and discuss how they could act as new molecular targets for the development of therapeutic approaches to treat pancreatic diseases.

The mtDNA nt7778 G/T polymorphism augments formation of lymphocytic foci but does not aggravate cerulein-induced acute pancreatitis in mice

A polymorphism in the ATP synthase 8 (ATP8) gene of the murine mitochondrial genome, G-to-T transversion at position 7778, has been suggested to increase susceptibility to multiple autoimmune diseases, including autoimmune pancreatitis (AIP). The polymorphism also induces mitochondrial reactive oxygen species generation, secretory dysfunction and β-cell mass adaptation. Here, we have used two conplastic mouse strains, C57BL/6N-mtAKR/J (B6-mtAKR; nt7778 G; control) and C57BL/6N-mtFVB/N (B6-mtFVB; nt7778 T), to address the question if the polymorphism also affects the course of cerulein-induced acute pancreatitis in mice. Therefore, two age groups of mice (3 and 12-month-old, respectively) were subjected to up to 7 injections of the secretagogue cerulein (50 µg/kg body weight) at hourly intervals. Disease severity was assessed at time points from 3 hours to 7 days based on pancreatic histopathology, serum levels of α-amylase and activities of myeloperoxidase (MPO) in lung tissue. A comparison of cerulein-induced pancreatic tissue damage and increases of α-amylase and MPO activities showed no differences between the age-matched groups of both strains. Interestingly, histological evaluation of pancreatic tissue of both untreated and cerulein-treated B6-mtAKR and B6-mtFVB mice also revealed the presence of infiltrates of immune cells surrounding ducts and vessels; a finding that is compatible with an early stage of AIP. After recovery from cerulein-induced pancreatitis (day 7 after the injections), 12-month-old B6-mtFVB mice but not B6-mtAKR mice displayed aggravated lymphocytic lesions. A comparison of 12-month-old mice with other age groups of both strains revealed that lymphocytic foci were largely absent in 3-month-old mice, while 24-month-old mice were more affected. Together, our data suggest that the mtDNA nt7778 G/T polymorphism does not aggravate cerulein-induced acute pancreatitis. Autoimmune-like lesions, however, may progress faster if additional tissue damage occurs.

How to win ATP and influence Ca(2+) signaling

This brief review discusses recent advances in studies of mitochondrial Ca(2+) signaling and considers how the relationships between mitochondria and Ca(2+) responses are shaped in secretory epithelial cells. Perhaps the more precise title of this review could have been "How to win ATP and influence Ca(2+) signaling in secretory epithelium with emphasis on exocrine secretory cells and specific focus on pancreatic acinar cells". But "brevity is a virtue" and the authors hope that many of the mechanisms discussed are general and applicable to other tissues and cell types. Among these mechanisms are mitochondrial regulation of Ca(2+) entry and the role of mitochondria in the formation of localized Ca(2+) responses. The roles of Ca(2+) signaling in the physiological adjustment of bioenergetics and in mitochondrial damage are also briefly discussed.

Calcium signaling in pancreatic ductal epithelial cells: an old friend and a nasty enemy

Ductal epithelial cells of the exocrine pancreas secrete HCO3(-) rich, alkaline pancreatic juice, which maintains the intraluminal pH and washes the digestive enzymes out from the ductal system. Importantly, damage of this secretory process can lead to pancreatic diseases such as acute and chronic pancreatitis. Intracellular Ca(2+) signaling plays a central role in the physiological regulation of HCO3(-) secretion, however uncontrolled Ca(2+) release can lead to intracellular Ca(2+) overload and toxicity, including mitochondrial damage and impaired ATP production. Recent findings suggest that the most common pathogenic factors leading to acute pancreatitis, such as bile acids, or ethanol and ethanol metabolites can evoke different types of intracellular Ca(2+) signals, which can stimulate or inhibit ductal HCO3(-) secretion. Therefore, understanding the intracellular Ca(2+) pathways and the mechanisms which can switch a good signal to a bad signal in pancreatic ductal epithelial cells are crucially important. This review summarizes the variety of Ca(2+) signals both in physiological and pathophysiological aspects and highlight molecular targets which may strengthen our old friend or release our nasty enemy.

Glycolytic ATP fuels the plasma membrane calcium pump critical for pancreatic cancer cell survival

Pancreatic cancer is an aggressive cancer with poor prognosis and limited treatment options. Cancer cells rapidly proliferate and are resistant to cell death due, in part, to a shift from mitochondrial metabolism to glycolysis. We hypothesized that this shift is important in regulating cytosolic Ca²⁺ ([Ca²⁺]_i), as the ATP-dependent plasma membrane Ca²⁺ ATPase (PMCA) is critical for maintaining low [Ca²⁺]_i and thus cell survival. The present study aimed to determine the relative contribution of mitochondrial versus glycolytic ATP in fuelling the PMCA in human pancreatic cancer cells. We report that glycolytic inhibition induced profound ATP depletion, PMCA inhibition, [Ca²⁺]_i overload, and cell death in PANC1 and MIA PaCa-2 cells. Conversely, inhibition of mitochondrial metabolism had no effect, suggesting that glycolytic ATP is critical for [Ca²⁺]_i homeostasis and thus survival. Targeting the glycolytic regulation of the PMCA may, therefore, be an effective strategy for selectively killing pancreatic cancer while sparing healthy cells.

Ethanol and its non-oxidative metabolites profoundly inhibit CFTR function in pancreatic epithelial cells which is prevented by ATP supplementation

Excessive alcohol consumption is a major cause of acute pancreatitis, but the mechanism involved is not well understood. Recent investigations suggest that pancreatic ductal epithelial cells (PDECs) help defend the pancreas from noxious agents such as alcohol. Because the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel plays a major role in PDEC physiology and mutated CFTR is often associated with pancreatitis, we tested the hypothesis that ethanol affects CFTR to impair ductal function. Electrophysiological studies on native PDECs showed that ethanol (10 and 100 mM) increased basal, but reversibly blocked, forskolin-stimulated CFTR currents. The inhibitory effect of ethanol was mimicked by its non-oxidative metabolites, palmitoleic acid ethyl ester (POAEE) and palmitoleic acid (POA), but not by the oxidative metabolite, acetaldehyde. Ethanol, POAEE and POA markedly reduced intracellular ATP (ATPi) which was linked to CFTR inhibition since the inhibitory effects were almost completely abolished if ATPi depletion was prevented. We propose that ethanol causes functional damage of CFTR through an ATPi-dependent mechanism, which compromises ductal fluid secretion and likely contributes to the pathogenesis of acute pancreatitis. We suggest that the maintenance of ATPi may represent a therapeutic option in the treatment of the disease.

Intraductal acidosis in acute biliary pancreatitis

Acute pancreatitis recently became the most common cause for hospitalization among gastrointestinal diseases. There is no specific therapy against the disease due to insufficient understanding of pathogenesis. Animal and in vitro models indicated that reduced pancreatic ductal bicarbonate secretion and consequent intraductal acidosis is an early event in acute pancreatitis, but human data are lacking. Therefore, our aim was to determine the luminal pH in the main pancreatic duct during acute pancreatitis in humans. Intraductal pH was measured in patients with acute biliary pancreatitis (n = 6) during endoscopic retrograde cholangio-pancreatography. Patients with common bile stones without pancreatitis (n = 5) and a patient with an adenoma of the papilla of Vater served as controls. The luminal pH was significantly lower in the group of acute biliary pancreatitis vs. controls (6.97 ± 0.13 vs. 7.79 ± 0.20). Our brief report shows for the first time that there is marked intraductal acidosis in acute biliary pancreatitis, which seems to worsen with time. Further clinical trials are needed to determine the exact roles of reduced intraductal pH in ABP.

Central role of mitochondrial injury in the pathogenesis of acute pancreatitis

Acute pancreatitis is an inflammatory disease with no specific treatment. One of the main reasons behind the lack of specific therapy is that the pathogenesis of acute pancreatitis is poorly understood. During the development of acute pancreatitis, the disease-inducing factors can damage both cell types of the exocrine pancreas, namely the acinar and ductal cells. Because damage of either of the cell types can contribute to the inflammation, it is crucial to find common intracellular mechanisms that can be targeted by pharmacological therapies. Despite the many differences, recent studies revealed that the most common factors that induce pancreatitis cause mitochondrial damage with the consequent breakdown of bioenergetics, that is, ATP depletion in both cell types. In this review, we summarize our knowledge of mitochondrial function and damage within both pancreatic acinar and ductal cells. We also suggest that colloidal ATP delivery systems for pancreatic energy supply may be able to protect acinar and ductal cells from cellular damage in the early phase of the disease. An effective energy delivery system combined with the prevention of further mitochondrial damage may, for the first time, open up the possibility of pharmacological therapy for acute pancreatitis, leading to reduced disease severity and mortality.

Bile acids induce pancreatic acinar cell injury and pancreatitis by activating calcineurin

Biliary pancreatitis is the leading cause of acute pancreatitis in both children and adults. A proposed mechanism is the reflux of bile into the pancreatic duct. Bile acid exposure causes pancreatic acinar cell injury through a sustained rise in cytosolic Ca(2+). Thus, it would be clinically relevant to know the targets of this aberrant Ca(2+) signal. We hypothesized that the Ca(2+)-activated phosphatase calcineurin is such a Ca(2+) target. To examine calcineurin activation, we infected primary acinar cells from mice with an adenovirus expressing the promoter for a downstream calcineurin effector, nuclear factor of activated T-cells (NFAT). The bile acid taurolithocholic acid-3-sulfate (TLCS) was primarily used to examine bile acid responses. TLCS caused calcineurin activation only at concentrations that cause acinar cell injury. The activation of calcineurin by TLCS was abolished by chelating intracellular Ca(2+). Pretreatment with 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (acetoxymethyl ester) (BAPTA-AM) or the three specific calcineurin inhibitors FK506, cyclosporine A, or calcineurin inhibitory peptide prevented bile acid-induced acinar cell injury as measured by lactate dehydrogenase leakage and propidium iodide uptake. The calcineurin inhibitors reduced the intra-acinar activation of chymotrypsinogen within 30 min of TLCS administration, and they also prevented NF-κB activation. In vivo, mice that received FK506 or were deficient in the calcineurin isoform Aβ (CnAβ) subunit had reduced pancreatitis severity after infusion of TLCS or taurocholic acid into the pancreatic duct. In summary, we demonstrate that acinar cell calcineurin is activated in response to Ca(2+) generated by bile acid exposure, bile acid-induced pancreatic injury is dependent on calcineurin activation, and calcineurin inhibitors may provide an adjunctive therapy for biliary pancreatitis.

Mitochondrial calcium in the life and death of exocrine secretory cells

The remarkable recent discoveries of the proteins mediating mitochondrial Ca(2+) transport (reviewed in this issue) provide an exciting opportunity to utilise this new knowledge to improve our fundamental understanding of relationships between Ca(2+) signalling and bioenergetics and, importantly, to improve the understanding of diseases in which Ca(2+) toxicity and mitochondrial malfunction play a crucial role. Ca(2+) is an important activator of exocrine secretion, a regulator of the bioenergetics of exocrine cells and a contributor to exocrine cell damage. Exocrine secretory cells, exocrine tissues and diseases affecting exocrine glands (like Sjögren's syndrome and acute pancreatitis) will, therefore, provide worthy research areas for the application of this new knowledge of the Ca(2+) transport mechanisms in mitochondria.

Review of experimental animal models of biliary acute pancreatitis and recent advances in basic research

Acute pancreatitis (AP) is a formidable disease, which, in severe forms, causes significant mortality. Biliary AP, or gallstone obstruction-associated AP, accounts for 30-50% of all clinical cases of AP. In biliary AP, pancreatic acinar cell (PAC) death (the initiating event in the disease) is believed to occur as acinar cells make contact with bile salts when bile refluxes into the pancreatic duct. Recent advances have unveiled an important receptor responsible for the major function of bile acids on acinar cells, namely, the cell surface G-protein-coupled bile acid receptor-1 (Gpbar1), located in the apical pole of the PAC. High concentrations of bile acids induce cytosolic Ca(2+) overload and inhibit mitochondrial adenosine triphosphate (ATP) production, resulting in cell injury to both PACs and pancreatic ductal epithelial cells. Various bile salts are employed to induce experimental AP, most commonly sodium taurocholate. Recent characterization of taurolithocholic acid 3-sulphate on PACs has led researchers to focus on this bile salt because of its potency in causing acinar cell injury at relatively low, sub-detergent concentrations, which strongly implicates action via the receptor Gpbar1. Improved surgical techniques have enabled the infusion of bile salts into the pancreatic duct to induce experimental biliary AP in mice, which allows the use of these transgenic animals as powerful tools. This review summarizes recent findings using transgenic mice in experimental biliary AP.

Regulation of acid-base transporters by reactive oxygen species following mitochondrial fragmentation

Mitochondrial morphology is determined by the balance between the opposing processes of fission and fusion, each of which is regulated by a distinct set of proteins. Abnormalities in mitochondrial dynamics have been associated with a variety of diseases, including neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease, and dominant optic atrophy. Although the genetic determinants of fission and fusion are well recognized, less is known about the mechanism(s) whereby altered morphology contributes to the underlying pathophysiology of these disease states. Previous work from our laboratory identified a role for mitochondrial dynamics in intracellular pH homeostasis in both mammalian cell culture and in the genetic model organism Caenorhabditis elegans. Here we show that the acidification seen in mutant animals that have lost the ability to fuse their mitochondrial inner membrane occurs through a reactive oxygen species (ROS)-dependent mechanism and can be suppressed through the use of pharmacological antioxidants targeted specifically at the mitochondrial matrix. Physiological approaches examining the activity of endogenous mammalian acid-base transport proteins in rat liver Clone 9 cells support the idea that ROS signaling to sodium-proton exchangers contributes to acidification. Because maintaining pH homeostasis is essential for cell function and viability, the results of this work provide new insight into the pathophysiology associated with the loss of inner mitochondrial membrane fusion.

Trypsin reduces pancreatic ductal bicarbonate secretion by inhibiting CFTR Cl⁻ channels and luminal anion exchangers

BACKGROUND & AIMS

The effects of trypsin on pancreatic ductal epithelial cells (PDECs) vary among species and depend on the localization of proteinase-activated receptor 2 (PAR-2). We compared PAR-2 localization in human and guinea-pig PDECs, and used isolated guinea pig ducts to study the effects of trypsin and a PAR-2 agonist on bicarbonate secretion.

METHODS

PAR-2 localization was analyzed by immunohistochemistry in guinea pig and human pancreatic tissue samples (from 15 patients with chronic pancreatitis and 15 without pancreatic disease). Functionally, guinea pig PDECs were studied by microperfusion of isolated ducts, measurements of intracellular pH and intracellular Ca(2+) concentration, and patch clamp analysis. The effect of pH on trypsinogen autoactivation was assessed using recombinant human cationic trypsinogen.

RESULTS

PAR-2 localized to the apical membrane of human and guinea pig PDECs. Trypsin increased intracellular Ca(2+) concentration and intracellular pH and inhibited secretion of bicarbonate by the luminal anion exchanger and the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel. Autoactivation of human cationic trypsinogen accelerated when the pH was reduced from 8.5 to 6.0. PAR-2 expression was strongly down-regulated, at transcriptional and protein levels, in the ducts of patients with chronic pancreatitis, consistent with increased activity of intraductal trypsin. Importantly, in PAR-2 knockout mice, the effects of trypsin were markedly reduced.

CONCLUSIONS

Trypsin reduces pancreatic ductal bicarbonate secretion via PAR-2-dependent inhibition of the apical anion exchanger and the CFTR Cl(-) channel. This could contribute to the development of chronic pancreatitis by decreasing luminal pH and promoting premature activation of trypsinogen in the pancreatic ducts.